With consequential news dominating the media in recent years – the pandemic, politics, the opioid crisis – it’s easy to forget that cannabis legalization was a hot topic not long ago, and many people worried the move toward cannabis legalization around the country would lead to dangerous increases in cannabis use.
Research efforts to gauge the impact of cannabis legalization on cannabis use focus primarily on individual states, risks posed to adolescents and minors, and use patterns and prevalence among adolescents. That makes sense: adolescence is when people who use cannabis often initiate use, and the impact of cannabis use on the developing adolescent brain is a primary concern among parents, policymakers, scientists, and the general population.
To learn more about the impact of marijuana use beginning during adolescence and early adulthood, please navigate to the blog section of our website and read this article:
The Impact of Long-Term Marijuana Use on IQ and Cognitive Function
If you don’t know about the consequences of long-term cannabis use on cognitive function, we recommend reading that piece: it includes information we all need to know about long-term cannabis use.
In this article, we’ll discuss the impact of cannabis legalization impact on cannabis use among adults, using data from a study published recently by Carnegie Mellon University.
Before we look at that data, let’s take a look at the broad details around the recent legalization movement.
Cannabis Legalization: Where, What, and When?
Here’s a quick review of decriminalization and legalization of cannabis in the U.S.:
Cannabis: Legal Status
- 1970s: decriminalized in 14 states
- 1990s: medical cannabis legalized in 21 states
- 2012 and 2024: recreational cannabis legalized in 19 states
Recreational cannabis is now legal in 19 states. Medical cannabis is legal in 38 states. Recreational and medical cannabis are both legal in Washington, DC, as well. This legalization movement should not surprise anyone, since it reflects our general attitudes toward cannabis. A recent survey from Pew Charitable Trusts confirms that a majority of people in the U.S support legalization for both medical and recreational use:
Cannabis: Overall Opinions on Legalization
- Always illegal: 10%
- Legal for medical use only: 30%
- Legal for recreational and medical use: 59%
- Declined to answer: 1%
Public opinion on legalization also mirrors public perception of the harms of marijuana use. The National Survey on Drug Use and Health (NSDUH) reports the following.
Cannabis: How Many People Think Cannabis Use* Causes Harm?
*Regular use defined as using cannabis once or twice a week*
- 2002: 51.3% of adults thought regular use was associated with great risk of harm
- 2012: 40.3% of adults thought regular use was associated with great risk of harm
- 2021: 25.7% of adults thought regular use was associated with great risk of harm
- 2022: 24.4% of adults thought regular use was associated with great risk of harm
This set of bullet points offers more confirmation that the legalization trend follows public opinion: as the years pass, and more states ease cannabis laws, fewer adults perceive cannabis as causing risk of harm.
Now let’s look at the results of that Carnegie Mellon study.
Cannabis Legalization and Cannabis Use Over Time
In this study – link above, in the introduction – researchers examined long-term data from the National Survey on Drug Use and Health (NSDUH) and the National Household Survey on Drug Abuse (NHSDA). Scientists analyzed results from surveys conducted between 1979-2022, which included over 1.6 million participants from a total of 27 nationwide surveys.
The research team highlighted data from four important years:
- 1979: First data available
- 1992: End of a period relatively conservative cannabis policies, 1980-1992
- 2008: Federal government declared a non-interference policy with state cannabis legalization
- 2022: Most recent available data
This report offers a much-needed update on the question of how the trend toward cannabis legalization impacted cannabis use. Here’s what they found:
Cannabis Use Trends: 1972-2022
- Past-year use:
- Lowest in 1992
- Rose gradually between 1992 and 2008
- Increased 120% between 2008 and 2024
- Daily use, 1992-2022:
- Increased 1500%
- 1992: 0.9 million reported daily/near daily cannabis use
- 2022: 14.7 million reported daily/near daily cannabis use
That’s the data we needed to see. Like the trends we reported above, the trend in use among adults aligns with the trend toward legalization: as legalization became more prevalent, use became more prevalent.
The researchers also compared recreational cannabis use to recreational alcohol use. Here’s what they found:
Cannabis Use Compared to Alcohol Use
- Among those reporting past-month cannabis use:
- 42% report daily/near daily use
- 28% report daily use
- Among those reporting past-month alcohol use:
- 11% reported daily/near daily use
- 3% reported daily use
That’s instructive.
Although 52.9 percent of adults 18+ report past-month alcohol use and 17.4 percent report past-month cannabis use – a difference of over 100 percent – far more monthly cannabis users also reported daily or near-daily use, when compared to monthly alcohol users who also reported daily or near daily use.
What the Study Means, How the Research Helps
Here’s how the study author, Dr. Jonathan Caulkins, characterizes these results:
“The enormous changes in rates of self-reported cannabis use, particularly of daily or near-daily use, suggest that changes in actual use have been considerable. It is striking that high-frequency cannabis use is now more commonly reported than is high-frequency drinking.”
And here’s how he describes the overall results of the study:
“These trends mirror changes in policy, with declines during periods of greater restriction and growth during periods of policy liberalization. But whichever way causal arrows point, cannabis use now appears to be on a fundamentally different scale than it was before legalization.”
What the study means is that across the board, nationwide, cannabis use has increased by a significant margin over the past several decades, with most increases occurring since 2008, when the trend toward legalization gathered momentum.
This research helps us by teaching us that we need to keep a close eye on people who report past-month cannabis use. The data shows they’re at increased risk of transitioning to daily or near-daily use, which could increase risk of cannabis use disorder, and – if daily use continues long-term – could also increase risk of cognitive impairment associated with chronic, long-term cannabis use.
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